1. Field of the Invention
The present invention relates to an image display apparatus.
2. Description of the Related Art
Japanese Patent Application Laid-Open No. 2000-75833 discloses a phosphor saturation correction method as gamma correction for faithfully displaying a color and contrasting of an original image signal about a luminance signal and a color signal in consideration of a γ property of a phosphor in a display.
The U.S. Pat. No. 6,307,327 discloses a pixel data correction method for controlling a visibility of a spacer by a field emission display. According to this pixel data correction method, defining a first region in the vicinity of a spacer and a second region not in the vicinity of the spacer, then, in order to prevent a viewer from seeing display unevenness caused by the spacer, pixel data to be transmitted to the first region is corrected in response to an intensity level of a light to be generated by a plurality of pixels in the first region in the vicinity of the spacer.
Japanese Patent Application Laid-Open No. 2005-301218 discloses the fact that a correction amount is a value reflecting a driving state of phosphors that are located around a phosphor to be corrected and a value such that adjustment in accordance with a no-linearity property between an input signal and the display of the phosphor is made based on a value of an input signal corresponding to the correction target phosphor.
Japanese Patent Application Laid-Open No. 2006-195444 discloses that the correction amount is changed for each of R, G, and B phosphors when carrying out correction in order to prevent the viewer from seeing the display unevenness caused by the spacer and the optimum correction amount is changed depending on the state of lighting.
An image display apparatus that can realize a more preferable image display is desired. In this case, the more preferable image display is image display having small image unevenness, for example.
At first, a beam and a halation will be described. When an electron emitted from an electron source collides with the phosphor, a beam is generated. Here in this specification, a beam means light generated by irradiation of electron emitted from an electron-emitting device corresponding to a phosphor. At the same time, the electron emitted by an electron-emitting device not only generates the beam but it also scatters elastically (FIG. 15). Then, backward scattered electron that is scattered around due to the elastic scattering flashes a surround phosphor. This light emission due to the backward scattered electron is referred to as halation. Further, a beam luminance indicates a luminance only due to beam lighting in the phosphor and the beam luminance does not include the light emission due to the backward scattered electron (FIG. 15).
The inventors of the present invention found that the increase amount of light emission generated when the same amount of the backward scattered electrons is added was different between the lighting phosphor and the no-lighting phosphor (FIG. 16). When the surround phosphors are lighted as shown in FIG. 16A, the amount of the backward scattered electrons is distributed almost uniformly in the target phosphor. However, comparing the halation light emission amount of the place where the beam is lighted with that of the place where the beam is not lighted in the same phosphor, it is determined that halation amount at the place where the beam is lighted is smaller than that at the place where the beam is not lighted (FIG. 16D). Thereby, it is also determined that the spacer unevenness is changed depending on the lighting state of the target phosphor and the optimum correction amount is also changed.
The inventors of the present invention found that a ratio between the luminance of the beam and the luminance of the halation was not always constant for the beam luminance but this ratio was changed depending on variation of the input value of a halation correction unit shown in FIG. 4 and FIG. 5 (FIG. 13). Checking a cause of this in detail, a relation between the luminance of the phosphor and the electric charge amount is represented by γ≠1 in a high electric charge region such as a lighting beam, however, it is represented by γ nearly equal 1 in a low electric charge region such as a halation (FIG. 14). Thereby, depending on a lighting state of pixels around the pixel to be corrected, a ratio of unevenness of the spacer or the like is changed. According to the conventional correction method, the above-described relation between the luminance of the phosphor and the electric charge amount is not considered.